Heated fluid, such as steam, can be injected into a subterranean formation to facilitate production of fluids from the formation. For example, steam may be used to reduce the viscosity of fluid resources in the formation, so that the resources can more freely flow into the well bore and to the surface. Generally, steam generated for injection into a well requires large amounts of energy such as to compress and/or transport air, fuel, and water used to produce the steam. Much of this energy is largely lost to the environment without being harnessed in any useful way. Consequently, production of steam has large costs associated with its production.